Energy analyzer of coaxial cylindrical type

ABSTRACT

A coaxial cylindrical type energy analyzer includes an input slit for admitting charged particles into an energy analyzing field, and a detecting slit for introducing into a detector charged particles which have passed through the analyzing field. The slits are coaxially disposed opposite to each other across.

United States Patent n91 Yanagisawa et al.

[451 Apr. 16, 1974 ENERGY ANALYZER OF COAXIAL CYLINDRICAL TYPE [75] Inventors: Akira Yanagisawa, Tokyo; Akira Fukuhara, Tachikawa; Katsuhisa Usami, l-iachioji, all of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Mar. 22, 1972 [21] Appl. No.: 237,126

[52] US. Cl. 250/49.5 AE [51] Int. Cl. H0lj 37/26 [58] Field of Search 250/495 AE, 49.5 PE

[56] 5 References Cited OTHER PUBLICATIONS High Sensitivity Auger Electron Spectrometer,

Palmberg et al. Applied Physics Letters, Vol. 15, No. 8, 10/15/69 pp. 254-255.

A Combined Energy and Angle Analyzer for Scattered Electrons, Harting, Review of Scientific Inst. Vol. 42, No.8 Aug. 1971 pp. l,l5ll,l56.

Primary Examiner-James W. Lawrence Assistant Examiner-C. E. Church Attorney, Agent, or Firm-Craig & Antonelli 5 7] ABSTRACT A coaxial cylindrical type energy analyzer includes an input slit for admitting charged particles into an energy analyzing field, and a detecting slit for introducing into a detector charged particles which have passed through the analyzing field. The slits are coaxially disposed opposite to each other across.

14 Claims, 9 Drawing Figures PATENTEDAPR 16 I974 3 805 "057 SHEEI 1 or 4 Q mimimmsmn I SQBOSLOST sum 2 0F 4 FIG. 4

FIG 5 TI-E N TENSITY DISTRIBUTION OF THE CHARGED PARTICLES Zdo Tl-E POSITION OF CHARGED PARTICLES AT THE DETECTING SLIT PATENTEDAPR 16 1914 31305057 saw u [If 4 ENERGY ANALYZER OF COAXIAL CYLINDRICAL TYPE BACKGROUND OF THE INVENTION This invention relates to an energy analyzer and more particularly to improvement in an energy analyzer of the coaxial cylindrical type.

DESCRIPTION OF THE PRIOR ART A charged particle energy analyzer of the coaxial double cylindrical type generally in use is operated in such a manner that ultraviolet rays, X-rays, gamma rays, or similar rays are applied to a sample, and the energy of charge particles, such as electrons and ions, emitted from the surface of the sample is analyzed.

In a conventional energy analyzer consisting of an outer cylindrical electrode and an inner cylindrical electrode disposed coaxial to each other, a voltage is applied across the outer and inner electrodes, and charged particles from the sample member are analyzed in the energy dispersion field located between said outer and inner electrodes.

Charged particles such as electrons and ions are admitted into the energy dispersion field (or energy analyzing field) through an input or incident slit disposed on the axis of the electrodes and focused into a beam with an acceptance angle of 2a through an angledefining slit disposed inside the inner cylindrical electrode. The beam then enters the energy analyzing field through an aperture disposed on the inner electrode. Charged particles in the energy dispersion field are dispersed according to the magnitude of energy of the individual particles, and the path of the charged particles in the dispersion field traces a parabolic curve. The charged particles passing through the dispersion field enter the detecting slit through another aperture disposed on the inner electrode and then reach the detector.

Among the charged particles passing through the dispersion field and subjected to energy dispersion, only thos having a specific amount of energy are selected by the detecting slit and admitted into the detector. Hence, the energy spectrum can be obtained when the strength of the field in the energy dispersion field, i.e., the voltage applied across the inner and outer electrodes, is varied, or the voltage for accelerating the charged particles before entering the incident slit is varied, thus varying the energy of the charge particles, and the number of the charged particles reaching the detector is measured.

According to the prior art, however, the charged particles from the incident slit are focused into a beam with an acceptance angle of 2a and driven aslant into the dispersion field. As a result, compared with the standard trajectory of the charged particles having a specific energy and driven at an incident angle the trajectory of the other charged particles deviates by an angle :ta from the incident angle 0 The charged particles are driven into the dispersion field at an incident angle of 0:01, and not only the charged particles having a specific energy but also those with an energy in the range corresponding to the incident angle 0 i a reach the detector, to cause aberration.

Such aberration, attributable to the acceptance angle a of the incident beam, can be reduced by narrowing the angle-defining slit and decreasing the angle a. However, the number of charged particles reaching the detector is reduced to result of a decrease in the intensity of the beam.

SUMMARY OF THE INVENTION An object of this invention is to provide a coaxial cylindrical type energy analyzer operable at a high intensity.

Another object of this invention is to provide a coaxial cylindrical type energy analyzer capable of carrying out energy analysis in a minimum amount of time.

With the above and other objects in mind, the present invention provides a coaxial cylindrical type energy analyzer in which a cylindrical incident slit and a cylin- BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram illustrating the principles of a conventional energy analyzer,

FIG. 2 is a schematic diagram illustrating the principles of the present invention,

FIG. 3 is a diagram showing the acceptance angle 7 of the beam incident upon a plane perpendicular to the common axis of the electrodes in the analyzer shown in FIG. 2,

FIG. 4 is a graphic representation showing the relationship between the incident angle 0,, necessary for second order focusing and the intensity K,, of the dispersion field, using a parameter 1 determined by the diameter of the slit.

FIG. 5 is a diagram showing a curve of the relationship between the position of the charged particles at the detecting slit and the intensity distribution of the charged particles reaching the detecting slit,

FIG. 6 is a diagram showing a curve of the relationship between the number of the charged particles passing through the detecting slit and the deviation of the particle energy from the normal value,

FIG. 7 is a contour diagram showing the intensity of the analyzer in operation optimized under the secondary focusing condition, and

FIG. 8(a) and 8(b) are sectional diagrams showing energy analyzers embodying this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS I of the electrodes. Charged particles, such as electrons and ions are emitted from a sample member (not shown) irradiated with ultraviolet rays, X-rays or similar rays. The charged particles are driven into the analyzer through the slit and are formed into a beam with an acceptance angle 2a, after passing through an angledefining slit 6 disposed annularly inside the inner electrode 1. The beam is driven into the energy dispersion field 3 between the inner and outer electrodes 1 and 2 by way of an aperture disposed on the inner electrode 1. In the dispersion field 3 the charged particles are dispersed according to the magnitudes of their energy and driven over a curved path into the space through an aperture circularly disposed on the inner electrode 1. Then the charged particles reach a detector 8 via a detecting slit 7 disposed on the axis.

Among the charged particles passing through the energy dispersion field and subjected to energy dispersion, those with a specific energy are selected by the detecting slit 7 and delivered to the detector 8. Hence, by varying the field strength of the dispersion field 3, i.e., the voltage V,, applied across the inner and outer electrodes 1 and 2, or by varying the voltage for accelerating the charged particles before entering the incident slit 5 and thereby varying the charged particle energy eV and at the same time measuring the number of the charged particles reaching the detector 8, an energy spectrum can be obtained.

In this case, the charged particles are driven into the dispersion field through the incident slit 5 in the form of beam with an acceptance angle of 2a and, therefore, the trajectory of the charged particles in general deviates from the standard trajectory 9 of the charged particles, with a specific energy and driven at the incident angle 0 by an angle a from the incident angle 0 The charged particles are driven into the dispersion field at an incident angle of 0 ia, and not only the charged particles having a specific energy but also those with an energy in the range corresponding to the incident angle 0:04 reach the detector 8, to cause aberration.

Such aberration which is attributed to the acceptance angle a of the incident beam can be reduced by narrowing the angle-defining slit 6 and decreasing the angle a. On the other hand, however, the number of charged particles reaching the detector 8 is reduced to result in a decrease in intensity.

It is assumed that the standard trajectory 9 is caused by the standard charged particles having a motion energy E, (E, eV entering from the incident point 10 on the axis of the incident slit 5 into the energy dispersion field 3 at an incident angle 0,, formed with the plane of the electrode, and the other trajectory is caused by the other charged particles having a motion energy E driven into the energy dispersion field through the angle-defining slit 6. Then the deviation f between the two trajectories in the axisl direction at the detecting slit 7 is given in terms of expansion into a power series as follows.

where Ci the aberration coefficient v Y2, D energy dispersivity E E, (l t) with an incident angle 0 0,, a

The aberration coefficient Ci and the value of energy dispersivity D are determined from Equation 1, when the incident angle is 0,, and the strength of the energy dispersion field is K a: Ve/Vp log b/a (where a the radius of the inner cylindrical electrode 1, and b the radius of the outer cylindrical electrode 2). When 0,, 42.307 and K 1.0310, the first and second order aberration coefficients with respect to a are both zero.

In the prior art, the incident slit 5 and the detecting slit 7 are disposed on the common axis of the cylindrical electrodes 1 and 2, and thus incident angle 0,, and analyzing field strength K which will satisfy the second order focusing condition with respect to a, are used. In this type of analyzer, because the charged particles are driven thereinto through the incident slit 5 on the axis and focused at the detection slit7 on the same axis, sufficient intensity can hardly be realized.

The present invention has overcome this difficulty by providing an analyzer operated on the principles which will be apparent when reading the following description.

In FIG. 2, an incident slit 25 and a detecting slit 27 are disposed circularly on two cylindrical members, respectively, with diameters 2ap and 2ap disposed in coaxial relation with a cylindrical electrode 21 and another cylindrical electrode 22. A voltage V,, is applied across the cylindrical electrodes 21 and 22, thereby forming an energy dispersion field in the space between the two electrodes.

The incident slit 25 and detecting slit 27 are separated from the axis 4 by ap, and ap respectively. The deviation fin the axial direction on the detecting slit 27 between the standard trajectory 9 of the charged particles with a specific energy, which particles are emitted from a point 10 on the incident slit 26, and the trajectory of other charged particles is expressed as where 7 represents half the acceptance angle of the beam incident upon the plane perpendicular to the axis and including the incident point 10 on the incident slit 5 of the standard trajectory 9, as shown in FIG. 3, and S denotes the axial distance between the incident point 10 of the standard trajectory on the incident slit 25 and the incident point of the other trajectory.

In this case also, the aberration coefficient Ci and the value of energy dispersivity D as in Equation (2) are determined according to the incident angle 0 of the beam and the dispersion field strength K When Ca 0 in Equation (3), the relation between the incident angle 0 and the field strength K which are to satisfy the first order focusing condition for a is determined. When the incident angle 0,, and the field strength K are varied under the first order focusing condition, it is possible to make the second order aberration coefficient Ca zero (Ca 0) at specific values of 0,, K even if the positions p and p of the incident slit and the detecting slit are arbitrarily determined, or these positions are located at arbitrary distances from the axis. When the values of 0,, and K, to satisfy the second order focusing condition are assumed to be 0 and K, the relation between 0 and K,, versus a parameter 1; will be as shown in FIG. 4, where n l (l/2) (p P2)- When the second order focusing condition 'is satistied, the deviation f between the standard trajectory and the other trajectory is expressed by Equation (3) based on Equation (2), assuming that higher order terms are negligible (practically, the deviation f is not appreciably affected by the higher order terms).

When the width of the incident slit 25 is 20:8 the 1 1 :ff J(u, t) du (4) This relation is illustrated in FIG. 6. In Equation (4), u and :1 represent the values normalized from the actual length based on the radius a of the inner electrode.

The resolving power of the analyzer is expressed by the base width of the spectral line I (t), i.e., the width t t,, and the intensity is given by the integral area of the spectral line I (t). The resolving power Aand the intensity L are expressed as A=2d +fmax+fmin...

L (2 8,, d a, yo sin B /D) X a where f max and f min are the maximum and minimum values, respectively of Equation (3) when S, a, y are varied in the variable range of 1 S i a, and yo which are determined by the individual slits.

The optimum values of S d a, and 7,, which determine the slit width and beam acceptance angle are selected so that the resolving power A is kept constant and the intensity L is maximized. These optimum values are calculated as follows by Lagranges method of undetermined multipliers.

When I A p. L (where t -an undetermined multiplier multiplier),

1 1+5 kao Note that the above calculations are based on the condition that The optimum condition for maximizing the intensity L under the condition that the resolving power A is constant is given by Equation (8) through (12). The double sign in each of these equations depends on the sign of p In other words, the intensity L under optimum conditions depends on whether the detecting slit is located above or below the axis with respect to the incident slit, or depends on the position of the detecting slit with respect to the incident slit. This principle is illustrated in FIG. 7 wherein the abscissa represents the position p of the incident slit with respect to the axis, and the ordinate the position p of the detecting slit. The curves show in contour the intensity L under the optimum condition when the resolving power of the analyzer is set at l X 10 When the position p of the detecting slit is negative, this means that the position of the detecting slit is opposite to the incident slit with respect to the axis. Namely, the focusing point (i.e., the position where the detecting slit is located) of the charged particles emitted from the incident slit is postioned opposite the incident slit across the axis.

As will be apparent from FIG. 7, in the coaxial cylindrical type energy analyzer used under the second order focusing condition, greater intensity L can be obtained by locating the detecting slit (i.e., the charged particle focusing point) opposite the incident slit with respect to the axis.

Thus, according to the invention, a highly practical energy analyzer free of the prior art problems is realized.

Referring to FIG. 8(a), there is schematically shown the structure of an energy analyzer embodying this invention wherein an outer cylindrical electrode 81 and an inner cylindrical electrode 82 with radii a and b, respectively, are disposed coaxial with each other, forming therebetween a space to serve as an energy dispersion field 83. Apertures 812 and 813 are disposed in the inner cylindrical electrode, through which apertures the charged particles to be analyzed pass.

A voltage V, whose magnitude can be varied is applied between the outer electrode 81 and the inner electrode 82. An incident slit 85 is disposed circularly on a cylindrical member with a diameter 2ap installed coaxial with the cylindrical electrodes 81 and 82. A detecting slit 87 is disposed circularly on a cylindrical member with a diameter 2ap installed coaxial with the cylindrical electrodes 81 and 82. An angle-defining slit 86 is disposed in the neighborhood of the aperture 812 inside the inner cylindrical electrode 82.

A focusing electrode 811 for introducing the charged particles from the detecting slit 87 into the detector 88 is disposed inside the inner cylindrical electrode 82. The numeral 814 denotes a sample member which is irradiated by ultraviolet rays, X-rays, gamma rays, a corpuscular beam or similar rays, whereby charged particles are produced. The detector 88 comprises in combination a scintillator and a photoelectronic multiplier to be operable at a high sensitivity.

This energy analyzer is operated in the following manner. The stream of charged particles emitted from the sample member 814 by way of the incident slit 85 is led into the space between the cylindrical electrodes through the aperture 812 at an incident angle 0,, determined by the angle-defining slit 86. In the energy dispersion field 83 the charged particles are dispersed according to the magnitudes of energy the individual charged particles possess. Then the charged particles pass through the aperture 813, forming a parabolic curve consisting of a standard trajectory and a general trajectory. The charged particles, after passing through the aperture 813, cross the axis 84 and converge at the detecting slit 87 located opposite the incident slit 85 across the axis. The charged particles detected by the detecting slit 87 are focused by the focusing electrode 811 and then introduced into the detector 88.

When the voltage V applied between the inner and outer cylindrical electrodes 81 and 82 is varied, only charged particles having a specific energy cross the axis and reach the detector, which then detects such charged particles. At the output of the detector, therefore, it becomes possible to measure the number of 40 charged particles and to obtain an energy spectrum.

According to this invention, as described above, the incident slit 85 is located apart from the axis, and the detecting slit 87 also is apart from the axis and detects, across the axis, the charged particles emitted from the incident slit 85. In this structure the positions of the incident slit 85'and detecting slit 87 can be expressed by p, and p respectively, and the values 1; of p and p can be suitably determined in the following ranges.

When, for example, p 0.55 and p 0.55, the value of 1 is 1. Hence, as shown in FIG. 4, the value of the incident angle 6,, and the value of the dispersion field strength K are:

Under this condition the aberration coefficients C03, C'y and Ca-y and energy dispersivity D are as follows:

'Ca 15.5 C72 0.4 C047 2.0

Table 1 shows the optimum values obtained by using these values. In the foregoing embodiment, the incident slit width 2S, and the detecting slit width 2d,, are based on the length along the axis of the analyzer (FIG. 2).

While in Table l the s e slit widths are indicated by S and d' of length perpendicular to the standard trajectory.

In comparison with the data in Table 1,Table Zjb e; low) shows those obtained in a conventional coaxial cylindrical typeenergy analyzer having the incident slit and the detecting slit disposed on the axis to each other. In this case, p, p 0 and, therefore, 1; 1.0 as in the foregoing embodiment wherein the incident slit and the detecting slit are disposed not coaxially. Namely, the values in Table 2 are obtained under the same focusing condition as in the foregoing embodiment of the invention.

Based on the results of Tables 1 and 2, the intensity of the conventional analyzer in which the incidentwt and the detecting slit are disposed coaxial with each other is compared with that of the analyzer of this innot limited to this embodiment. For example, only the detecting slit may be disposed on the axis, and' the charged particles emitted from the incident slit may be detected at the point where the charged particles cross the axis. In this case, p 0, and the values of p and p are suitably determined in the following ranges.

FIG. 8(b) shows another embodiment of the invention wherein the detecting slit 87 is disposed on the axis 84, and the charged particles are focused at the point where the charged particles cross the axis 84. In FIG. 8(b), the detecting slit portion is essentially illustrated in connection with the analyzer as in FIG. 8(a), and the similar parts are not shown.

In the foregoing embodiments, the incident slit and the detecting slits are both cylindrical. Instead, these slits may be disposed on suitable plates.

While a few embodiments of the invention have been illustrated and described-in detail, it is particularly understood that invention is not limited thereto or thereby.

We claim:

1. An energy analyzer of the coaxial cylindrical type for analyzing the energy of charged particles, comprising:

an outer cylindrical electrode;

an inner cylindrical electrode disposed coaxially with said outer electrode and forming a space between said outer and inner electrodes, said inner electrode having a first aperture and a second aperture serving as an inlet and an outlet respectively, said first aperture allowing charged particles to enter said space, and said second aperture allowing such charged particles proceeding along a curved path through said space to emerge from said space and enter said inner cylindrical electrode;

means for applying a voltage between said outer and inner electrodes;

an acceptance angle slit disposed near said first aperture, so that a predetermined adjustable angle is formed to guide the charged particles;

a first slit member having an incident slit and disposed in said inner cylindrical electrode at a predetermined distance from the axis of said first and second cylindrical electrodes, for allowing the charged particles to go aslant into said first aperture;

a second slit member having a detecting slit and disposed in said inner cylindrical electrode at a predetermined distance from the axis of said first and second cylindrical electrodes in such a manner that the charged particles proceeding along the curved path through said space and said second aperture are focused at the detecting slit after the charged particles cross said axis; means disposed on said axis for detecting the charged particles which have passed through said detecting slit; and

focussing means disposed between said detecting slit and said detecting means for focussing, on the axis, the charged particles which have been converged and emitted from said detecting slit.

2. An energy analyzer of the coaxial cylindrical type as defined in claim 1, wherein said second slit member is disposed so that the charged particles cross the axis and are concurrently focused on the-axis.

3. An energy analyzer of the coaxial cylindrical type for analyzing the energy of charged particles, comprisa first cylindrical hollow electrode of a first diameter having an axis;

a second cylindrical hollow electrode of a second diameter less than said first diameter coaxially disposed within said first cylindrical electrode so as to form a space between said first and second electrodes, said second electrode having first and second apertures formed therein and spaced in an axial direction with respect to each other;

means, coupled to said first and second electrodes,

for applying a potential difference therebetween;

means, disposed within said second electrode adjacent the portion thereof wherein said first aperture is formed, for supplying charged particles to be introduced toward said first aperture in said second electrode, said charged particle supplying means comprising a first cylindrically-shaped member coaxially disposed within said second electrode and having a first slit formed therein, in the direction of said axis, for permitting charged particles within said member to be directed toward said first aperture at a predetermined angle;

means, disposed within said second electrode adjacent the portion thereof wherein said second aperture is formed, for detecting charged particles which have been introduced toward said first aperture and have travelled along a curved path within the space between said first and second electrodes and have passed through said second aperture toward the hollow interior of said second electrode, said charged particle detecting means comprising a detecting element on said axis and a member, having a second slit therein, said seocnd slit, on which the charged particles are focused, being formed along said axis, adjacent said detecting element, for controlling the direction of incidence of charged particles upon said detecting element; and

focussing means disposed between said second slit and said detecting element for focussing on the axis the charged particles which have been converged and emitted from said second slit.

4. An energy analyzer of the coaxial cylindrical type as defined in claim 3, wherein said detecting means comprises a second cylindrically shaped member coaxially disposed within said second electrode within which said detecting element is disposed, said second slit being formed in said second cylindrically shaped member.

5. An energy analyzer of the coaxial cylindrical type as defined in claim 4, wherein said second cylindrically shaped member is axially disposed with respect to said second aperture so that charged particles passing through said second aperture intersect said axis after passing through said second slit.

6. An energy analyzer of the coaxial cylindrical type as defined in claim 3, further including a focusing electrode disposed within said second electrode and surrounding a portion of said member for directing charged particles which have passed through said second aperture and said second slit to said detecting element.

7. An energy analyzer of the coaxial cylindrical type as defined in claim 3 wherein said detecting means comprises a second cylindrically shaped member coaxially disposed within said second electrode and is axially spaced from said detecting element.

8. An energy analyzer of the coaxial cylindrical type as defined in claim 7, further including a focusing electrode disposed within said second electrode and surrounding a portion of said second cylindrically shaped member for directing charged particles which have passed through said second aperture and said second slit to said detecting element.

9. An energy analyzer of the coaxial cylindrical type as defined in claim 8, wherein said second cylindrically shaped member is axially spaced with respect to said second aperture and said detecting element so that charged particles passing through said second aperture cross said axis before passing through said second slit.

10. An energy analyzer of the coaxial cylindrical type as defined in claim 3, wherein member having said second slit comprises a plate member disposed on said axis and being axially separated from said detecting element.

ond slit.

13. An energy analyzer of the coaxial cylindrical type as defined in claim 3, further including at least one angle defining slit member coaxially disposed between said charged particle introducing means and said first aperture in said second electrode.

14. An energy analyzer of the coaxial cylindrical type as defined in claim 13, wherein said at least one angle defining slit member comprises a pair of angle defining slit members separated from said axis at different respective distances. 

1. An energy analyzer of the coaxial cylindrical type for analyzing the energy of charged particles, comprising: an outer cylindrical electrode; an inner cylindrical electrode disposed coaxially with said outer electrode and forming a space between said outer and inner electrodes, said inner electrode having a first aperture and a second aperture serving as an inlet and an outlet respectively, said first aperture allowing charged particles to enter said space, and said second aperture allowing such charged particles proceeding along a curved path through said space to emerge from said space and enter said inner cylindrical electrode; means for applying a voltage between said outer and inner electrodes; an acceptance angle slit disposed near said first aperture, so that a predetermined adjustable angle is formed to guide the charged particles; a first slit member having an incident slit and disposed in said inner cylindrical electrode at a predetermined distance from the axis of said first and second cylindrical electrodes, for allowing the charged particles to go aslant into said first aperture; a second slit member having a detecting slit and disposed in said inner cylindrical electrode at a predetermined distance from the axis of said first and second cylindrical electrodes in such a manner that the charged particles proceeding along the curved path through said space and said second aperture are focused at the detecting slit after the charged particles cross said axis; ''''means disposed on said axis for detecting the charged particles which have passed through said detecting slit; and focussing means disposed between said detecting slit and said detecting means for focussing, on the axis, the charged particles which have been converged and emitted from said detecting slit.''''
 2. An energy analyzer of the coaxial cylindrical type as defined in claim 1, wherein said second slit member is disposed so that the charged particles cross the axis and are concurrently focused on the axis.
 3. An energy analyzer of the coaxial cylindrical type for analyzing the energy of charged particles, comprising: a first cylindrical hollow electrode of a first diameter having an axis; a second cylindrical hollow electrode of a second diameter less than said first diameter coaxially disposed within said first cylindrical electrode so as to form a space between said first and second electrodes, said second electrode having first and second apertures formed therein and spaced in an axial direction with respect to each other; means, coupled to said first and second electrodes, for applying a potential difference therebetween; means, disposed within said second electrode adjacent the portion thereof wherein said first aperture is formed, for supplying charged particles to be introduced toward said first aperture in said second electrode, said charged particle supplying means comprising a first cylindrically-shaped member coaxially disposed within said second electrode and having a first slit formed therein, in the direction of said axis, for permitting charged particles within said member to be directed toward said first aperture at a predetermined angle; means, disposed within said second electrode adjacent the portion thereof wherein said second aperture is formed, for detecting charged particles which have been introduced toward said first aperture and have travelled along a curved path within the space between said first and second electrodes and have passed through said second aperture toward the hollow interior of said second electrode, said charged particle detecting means comprising a detecting element on said axis and a member, having a second slit therein, said seocnd slit, on which the charged particles are focused, being formed along said axis, adjacent said detecting element, for controlling the direction of incidence of charged particles upon said detecting element; and ''''focussing means disposed between said second slit and said detecting element for focussing on the axis the charged particles which have been converged and emitted from said second slit.''''
 4. An energy analyzer of the coaxial cylindrical type as defined in claim 3, wherein said detecting means comprises a second cylindrically shaped member coaXially disposed within said second electrode within which said detecting element is disposed, said second slit being formed in said second cylindrically shaped member.
 5. An energy analyzer of the coaxial cylindrical type as defined in claim 4, wherein said second cylindrically shaped member is axially disposed with respect to said second aperture so that charged particles passing through said second aperture intersect said axis after passing through said second slit.
 6. An energy analyzer of the coaxial cylindrical type as defined in claim 3, further including a focusing electrode disposed within said second electrode and surrounding a portion of said member for directing charged particles which have passed through said second aperture and said second slit to said detecting element.
 7. An energy analyzer of the coaxial cylindrical type as defined in claim 3 wherein said detecting means comprises a second cylindrically shaped member coaxially disposed within said second electrode and is axially spaced from said detecting element.
 8. An energy analyzer of the coaxial cylindrical type as defined in claim 7, further including a focusing electrode disposed within said second electrode and surrounding a portion of said second cylindrically shaped member for directing charged particles which have passed through said second aperture and said second slit to said detecting element.
 9. An energy analyzer of the coaxial cylindrical type as defined in claim 8, wherein said second cylindrically shaped member is axially spaced with respect to said second aperture and said detecting element so that charged particles passing through said second aperture cross said axis before passing through said second slit.
 10. An energy analyzer of the coaxial cylindrical type as defined in claim 3, wherein member having said second slit comprises a plate member disposed on said axis and being axially separated from said detecting element.
 11. An energy analyzer of the coaxial cylindrical type as defined in claim 10, further including a focusing electrode disposed within said second electrode and surrounding a portion of said plate for directing charged particles which have passed through said second aperture and said second slit to said detecting element.
 12. An energy analyzer of the coaxial cylindrical type as defined in claim 11, wherein said plate is axially displaced with respect to said second aperture and said detecting element, so that charged particles passing through said second aperture cross said axis at said second slit.
 13. An energy analyzer of the coaxial cylindrical type as defined in claim 3, further including at least one angle defining slit member coaxially disposed between said charged particle introducing means and said first aperture in said second electrode.
 14. An energy analyzer of the coaxial cylindrical type as defined in claim 13, wherein said at least one angle defining slit member comprises a pair of angle defining slit members separated from said axis at different respective distances. 